In general, a silicon wafer may be manufactured by growing a silicon single-crystal ingot using the Czochralski method (CZ method), slicing the silicon ingot using a wire saw to obtain a sliced wafer, and performing lapping, etching, cleaning and polishing processes on the sliced wafer.
In the polishing process, both surfaces of the sliced wafer are polished using a double-side polishing apparatus, thereby obtaining a flattened silicon wafer.
The wafer polishing speed may vary for processing tools, such as a polishing cloth and a carrier, and deterioration of a material whenever the polishing process is performed. Therefore, in the case in which the polishing process is performed for a fixed time period, the thickness of the polished wafer may vary due to variation in the polishing speed attributable to the above-mentioned causes. It is necessary to measure the thickness of the wafer that is being polished and to adjust the polishing speed simultaneously therewith.